This invention relates to apparatuses for regulating the flow of air in a conduit, particularly for air-conditioning systems in motor vehicles.
The Applicant has previously proposed a apparatus of this kind in European Patent Application EP-A 0 895 885 comprising a support structure forming a passage section of a flow of air, flap means pivotally mounted on said support structure between a closed position and an open position, elastic means for recalling the flap means towards one of two said positions and shape memory actuators to control a movement of said flap means towards the other of said positions.
The use of actuators made of shape memory metallic alloys, typically nickel and titanium, is known and described in technical literature. These means are deformed when a certain predetermined transition temperature is reached, in the order of 100xc2x0 C., for example. In the aforesaid solution, the shape memory actuator consists of a torsion bar connected to a baffle flap, which is activated by the passage of electrical current.
The objective of this invention is to attain a apparatus of the type illustrated above, which structure is extremely simple and compact and which is efficient, in which the shape memory actuator is integrated in the structure of the apparatus.
In order to attain this result, this invention relates to a apparatus, which characteristics are described at the beginning of this description, and which is characterised in that it comprises a frame comprising two longer, parallel distanced sides and two end sides, which connect the two longer sides, so to create a window for the passage of air, in that said flap comprises a plurality of Venetian blind slats pivotally mounted between the two opposite sides of the frame, which are also connected to a mobile actuator rod along one of said sides, in that said elastic means are arranged between said actuator rod and said frame, and in that said shape memory actuator means comprise:
at least one wire made of metallic shape memory alloy, arranged in parallel to said actuator rod and having one end connected to the rod and the other end connected to the frame, the actuator rod and wire assembly being consequently substantially integrated in the structure of the frame,
means for supplying electrical current to the wire, so to heat it and shorten it by shape memory effect,
actuator rod position sensor and electronic control means for controlling the electrical power means, according to an external control signal of the apparatus and according to the output signal of said sensors.
Thanks to these characteristics, the apparatus according to this invention presents and extremely simple and compact structure, with the shape memory actuator completely integrated in the structure of the apparatus.
A typical application of the apparatus according to the invention is for regulating the passage of air through a conduit in a air-conditioning or ventilation system of a motor vehicle. In home position, the apparatus is held in one of its two extreme positions (which can be either the all-open position or the all-closed position) by the elastic means recalling the actuator rod. In operative position, the apparatus is located in a position which is determined by the control set by the driver by means of a corresponding control apparatus arranged on the dashboard of the motor vehicle. When said control apparatus is operated, the electronic control unit supplies electrical power to the shape memory wire, which heats up and shortens, causing the actuator rod to move in the direction of the position opposite to the home position. The sensor means of the actuator rod signal this position to the electronic control unit, which is thus capable of controlling the supply of electrical power to the shape memory wire so to keep the pivoting slats in the position corresponding to the control operated by the user.
In a preferred form of embodiment, said sensor means consists of a potentiometer, comprising an electrical track, connected to the frame of the apparatus, and a slider, which co-operates with the electrical track and is connected to the actuator rod. Preferably, two sets of pivoting slats are to be arranged and connected to the actuator rod so to turn simultaneously in opposite directions following the movement of the actuator rod. This structure is preferable to attain a uniform, symmetric flow of air through the conduit in which the apparatus according to this invention is mounted.